Differential Thermal Analysis Methods Research Articles

PHYSICO-CHEMICAL ANALYSIS OF QUARTZ SAND AND TECHNOLOGICAL WASTE USED AS A MAIN RAW MATERIAL FOR GLASS PRODUCTION

The composition and structure of Sherobod quartz sand and man-made waste were fully investigated using chemical, scanning electron microscope, X-ray, infrared spectroscopic and differential thermal analysis methods. It was found that the content of lead and manganese oxides in Handiza lead concentrate and manganese waste is 25 - 26 %, respectively, and silicon oxide in Sherabad quartz sand is more than 80 %. According to the results of chemical and physico-chemical analyzes of Sherabad quartz sand and man-made waste, it was found that they can be added as glass components by cleaning them from various additives.

THE METHOD OF DIFFERENTIAL THERMAL ANALYSIS IN STUDIES OF THE SOLID PULVERIZED FUEL DESTRUCTION AT A HIGH HEATING RATE

An analysis of publications containing information on the differential thermal analysis (DTA) method history, its essence and some aspects of practical use for the analysis of of solid fuel thermal destruction and combustion was carried out. A method of laboratory research based on the principles of DTA, characterized by a high heating rate (up to 2000 degr/min), is proposed. The possibility of using the proposed technique for comparative analysis of thermal destruction the kinetics for pulverized coal fuel (PVP) mixtures blown into blast furnaces to replace coke is shown.

The Use of the Catalysts Based on Coal Ash Microsphere and Chrysotile in the Thermal Destruction of Primary Coal Tar

In order to evaluate the possibility of using different catalysts prepared for the hydrogenation process of primary coal tar, the method of differential thermal analysis was used, which allows to determine the kinetic parameters of thermal destruction, such as the rate constant, activation energy, and pre-exponential multiplier. The effect of catalysts on characteristics of mass loss during heating of "Shubarkol Komir" JSC primary coal tar at a constant speed (20 K/min) in a nitrogen medium has been considered. Microsphere, NiO/microsphere, CoO/microsphere, chrysotile and NiCo/chrysotile have been taken as catalytic additives. In the presence of the catalysts, the rate of thermal destruction of primary coal tar increases in the following order: CoO/microsphere < NiO/microsphere < NiCo/chrysotile. While microsphere catalysts extend the range of thermal destruction, chrysotile catalysts lead to the rapid completion of the destruction process. This fact is characterized by the formation of bonds between catalytic additives and primary coal tar. It is important to determine such parameters that affect on the activation energy and macrokinetics of the thermal decomposition process for prediction of catalyst activity during hydrogenation of heavy hydrocarbon raw materials.

Phase equilibrium investigations and thermodynamic modeling of the HfO2–Ta2O5 system

AbstractThe HfO2–Ta2O5 system was investigated using two distinct methods: the equilibration method at temperatures ranging from 1 573 to 1 873 K and the differential thermal analysis method up to 2 473 K. To identify the phases, X‐ray diffraction (XRD) and scanning electron microscopy with energy‐dispersive X‐ray spectroscopy (SEM/EDX) were employed. The temperature of the eutectic reaction L→Hf6Ta2O17+Ta2O5 was measured to be 2 052 K and the eutectic composition to be 66.7 mol.% Ta2O5. The peritectic reaction L+HfO2→Hf6Ta2O17 was observed at a temperature of 2 287 K. The heat capacity of the Hf6Ta2O17 phase was measured using differential scanning calorimetry from 240 to 1 300K. The thermodynamic database for the HfO2–Ta2O5 system was derived.

CHEMICAL STABILITY OF CELLULOSE NITRATES: REVIEW

The results of the analysis of literature data on updated methods for determining the chemical stability of cellulose nitrates are presented. The relevance of research is due to the need to control the operation and storage of a widespread component of solid rocket fuels and explosive compositions. The criterion for chemical resistance is the value of the decomposition rate or the time dependence of the degree of decomposition of the sample. It is shown that methods for assessing the chemical resistance of cellulose nitrates are based on determining the rate of its thermal decomposition, which is measured by a specific parameter accompanying decomposition. These parameters include weight loss, amount of gaseous decomposition products released, decomposition temperature or thermal effects. Studies are carried out at elevated temperatures and allow you to control the magnitude or rate of change in the parameter that accompanies thermal decomposition. The possibility of using modern analytical methods for evaluating chemical resistance is shown: differential scanning calorimetry, thermogravimetric analysis, chemiluminescent analysis, infrared spectroscopy, high-performance liquid and thin-layer chromatography, gas chromatography, electron paramagnetic resonance, mass spectrometry, X-ray diffraction analysis. The preference for methods of differential scanning calorimetry or differential thermal analysis is substantiated. The results of studies on improving the chemical resistance of cellulose nitrates and compositions based on it with the use of new stabilizers of the aniline series, stabilizers of natural origin with the advantage of the latter on the examples of curcumin and lignins are presented. Due to the insufficient stability of cellulose nitrates, stabilizers added to the formulation of explosive compositions lengthen the induction period of the decomposition of nitro compounds and do not allow the development of the autocatalytic decomposition stage. Methods for determining the chemical stability of cellulose nitrates obtained from alternative sources of raw materials are presented. For citation: Vdovina N.P., Korchagina А.А., Budaev I.А. Chemical stability of cellulose nitrates: Review. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 5. P. 6-20. DOI: 10.6060/ivkkt.20236605.6725.

Effect of electrothermopolarization on thermal properties of compositions based on polypropylene and MnO2

Information about the internal structure can also be obtained by studying the thermal properties of composites with low molecular weight additives in the low and high temperature range.In this work, by studying the thermophysical properties of PP-based MnO2 composites after exposure to an electric field, we will look at how the additive changes the properties and determine the processes of thermal degradation after aging. Differential thermal analysis (DTA) or thermospectroscopy method is based on measuring the thermal effect when heating or cooling the test substance depending on the temperature. This method makes it possible to quantify the temperature of various transitions with high accuracy. Also that polymer and polymer composite aging relate to the high local anisotropy of force field due to sharp difference of intramolecular and intermolecular interaction forces. By derivatographic method polypropylene films (PP) exposed to electrothermoplarization filled by MnO2 to the extent of 0.5 and 1vol.% have been investigated. By electrothermoplarization E=7×106V/m as a result of aging PP matrix crystals part amorphism is taken place and thermal stability. It is established that electric intensity leads as to the complete amorphism of PP+0.5vol.%MnO2 composition so the complete depolymerization followed by volatilization of formed intermediate products to the extent of 100%.

Structure and properties of modified shungite concrete during electrode heating

Concrete composition modifying by different electrically conductive components is one of less laborious but relatively effective methods between wide variety of electrode concrete heating effectiveness improvement methods. The purpose of this study is investigation of special aspects of cement systems modified by powdered shungite (Ssp 400 m2/kg) in combination with active mineral and plasticizing admixtures that harden under electrode heating at below zero temperatures. By the method of differential thermal analysis anomaly of exothermic reaction of cement stone specimens was discovered, that is due to formation of hydrated calcium silicate С2SH (A) discovered by the method of quantitative XRDA, and is verified by results received from scanning electron microscopy method, which among other factors provides higher strength and low permeability to these composites. Stability of cement systems modified by shungite and curing under electrode heating has been proved.

Synthesis of BaSnO3 as a Highly Dispersed Additive for the Preparation of Proton-Conducting Composites

The process of thermolysis of barium hydroxostannate BaSn(OH)6 as a precursor for preparing barium stannate BaSnO3 has been investigated using the method of differential thermal analysis. Thermal decomposition products of the precursor were characterized using X-ray diffraction, IR spectroscopy, low-temperature nitrogen adsorption, and scanning electron microscopy. It was shown that dehydration at nearly 270 °C resulted in the formation of an X-ray amorphous multiphase product, from which single-phase barium stannate crystallized at temperatures above 600 °C. The synthesized barium stannate was used as a functional additive to prepare composite proton electrolytes in the CsHSO4-BaSnO3 system. The structural and transport properties of the obtained system were investigated. It is shown that the highly conductive state of the salt is stabilized in a wide range of temperatures. High conductivity values of composite solid electrolytes in the medium temperature range create the possibility of their use as solid electrolyte membrane materials.

Studying the properties of ash and slag waste for use in the manufacture of construction products

Purpose. The research purpose is to study the physical-chemical properties of ash and slag waste generated during the coal combustion at the Ekibastuz field in Kazakhstan, to determine the possibility of using waste as a secondary resource to reduce the negative human impact on the environment. Methods. The research uses the methods of X-ray phase and differential thermal analysis, as well as chemical analysis. The X-ray phase analysis makes it possible to determine the phase composition and structure of ash and slag wastes, while differential thermal analysis is used to study their behavior with temperature changes. A chemical analysis is performed to determine the composition of ash and slag. Findings. The chemical and granulometric composition of ash and slag waste from the Ekibastuz field coal combustion has been determined. Analysis of the ash chemical composition showed that its main components are silicon and aluminum oxides, as well as a significant amount of iron oxide. The results obtained confirm the possibility of using ash and slag waste as a secondary raw material to reduce the negative impact on the environment. Originality. It has been revealed that the thermal conductivity, ultimate strength and water-absorption of ceramic brick samples depend on the amount of ash added and the firing temperature. The possibility of obtaining building materials with minimum cement content has also been substantiated, which is a new and promising approach, given the high cost of cement as the main building material. Practical implications. The practical value of the research is in solving environmental problems associated with the use of ash and slag waste. Using these wastes as a secondary raw material, it is possible to reduce the anthropogenic burden on the environment, as well as the volume of ash dumps. In addition, vacant land previously occupied by ash and slag mixtures can be used for economic purposes.

Influence of electric field on the thermal properties of PP+NC nanocomposites for environmental chemistry application

Using Differential Thermal Analysis (DTA) method the thermal-physical properties of nanocomposites PP+NC for environmental and environmental chemistry applications were studied and the thermal-destruction processes after aging in an electric field were determined. The influence of various external factors (strong electric field, electric discharge, temperature, radiation, etc.) on polymers and composites based on polymers penetrates into the deep layers of the matrix and leads to the destruction and reconstruction of the structure. Changes in the ratio of crystalline and amorphous phase occur due to the formation of an interlayer crystalline phase in the matrix. In this regard, the thermal properties of pure PP and PP+2.0% NC nanocomposites were investigated using the derivatographic method to study the influence of the electric field on the aging process, melting temperature, and crystallization rate and depolymerization process.

SYNTHESIS AND PROPERTIES OF THE COORDINATION COMPOUND OF CALCIUM STEARATE WITH THIOCARBAMIDE

The complex compound of calcium stearate salt with thiourea was synthesized by mechanochemical method. The composition of the resulting compound was studied using the method of elemental analysis. For the first time, crystallographic data of the compound were obtained using X-ray phase analysis. The stability of the complex compound was determined using the method of differential thermal analysis

Different Approach to Thermodynamic Description of Bi-Te Binary System

The aim this work was the reinvestigation of phase equilibria in Bi-Te system. The as-cast and long-time equilibrated alloys of Bi-Te binary system were analysed by scanning electron microscopy, X-ray diffraction (XRD) and differential thermal analysis (DTA) methods. The primary solidified phases were identified for as-cast samples. The existence of the four intermetallic phases: Bi2Te3, BiTe, Bi2Te, Bi7Te3 was confirmed. Three of them melt incongruently in peritectic reactions. The model parameters of all phases in this system were assessed by optimization using available data by Calphad method. The stabilisation of these phases in other ternary systems was discussed taking into consideration its future application in thermodynamic description of Ag-Bi-Te ternary system.

An investigation of AlN nanoparticles by DTA and DTG methods

Differential thermal analysis (DTA) and differential thermal gravimetry (DTG) studies at different heating rates of were considered for AlN nanoparticles. The free Gibbs energy in the temperature range of 300÷1400 K is determined at 5, 10, 15 and 20 K/min heating rates. Experiments were separately carried out in both heating and cooling processes and obtained results were analyzed in detail. The enthalpy and entropy of the system composed of nano AlN particles at different thermal treatment rates were calculated (theoretical calculations were justified by experimental results). The values acquired from the experimental results were compared for all thermophysical parameters at different thermal treatment rates.

PROPERTIES OF GLASSES IN THE Ag2S–GeS2–As(Sb)2S3 SYSTEMS

The characteristic temperatures for individual glass samples of quasi-ternary systems Ag2S–GeS2–As(Sb)2S3 were determined by differential thermal analysis method. Obtained data show that the glass transition temperature of the alloys is in the range typical of chalcogenide glasses. It was established that the glass transition temperature increases with the modifier content in the range of 402-421 K and 373-438 K for the Ag2S–GeS2–As(Sb)2S3 systems, respectively. For the constant Ag2S concentration, the value of the glass transition and crystallization temperatures increases with the content of germanium (IV) sulfide. The reduced glass transition temperature Tgr was calculated from obtained results which lies in the range of 0.62-0.73 and 0.59-0.70 for the glasses of the Ag2S–GeS2–As(Sb)2S3 systems, respectively, which indicates the high capacity of the samples to glass formation. Optical absorption spectra were measured at 297 K. The band gap energy Eg of the glasses of the Ag2S–GeS2–As(Sb)2S3 systems was estimated from the data on the spectral distribution of the absorption coefficient in the region of the absorption edge. It was determined that the absorption edge shifts to longer wavelengths with the increase of the GeS2 content in glasses, while the energy position of the absorption edge increases. Ade crease in the band gap energy is observed for all glass samples when a modifier is introduced into the glass-forming matrix. The characteristic energy of the degree of tailing of the absorption edge is in the range from 0.066 to 0.079 eV for all studied glass samples.
 Keywords: сhalcogenide glasses; quasi-ternary systems; glass-formation; characteristic temperatures; band gap energy.

PHASE EQUILIBRIUM STATES IN A TWO-COMPONENT DIPHENYL-n-NONADECANE SYSTEM

The melting curves of the diphenyl-n-nonadecane system were calculated using the Schroeder equation and using the UNIFAC and UNIFAC Dortmund methods. The calculation results showed that the diphenyl-n-nonadecane system is eutectic. The compositions experimentally studied by the method of differential thermal analysis and calculated by the indicated methods are not eutectic. Individual substances and 9 compositions within the studied system were experimentally studied using a differential scanning calorimeter. Based on the data obtained, a phase diagram was constructed, including one single-phase field above the liquidus curve and 4 two-phase fields – α-n-C19H40+(Ph)2, β-n-C19H40+(Ph)2, L+n-C19H40, L+(Ph)2. The predominant branch of the liquidus curve belongs to the more refractory component, diphenyl. In the solidus at a temperature of 18.7 °C, a polymorphic transformation α-n-C19H40 ⇆ β-n-C19H40 is noted, which coincides with the literature temperature data. The heating DTA curve of the eutectic alloy showed two endoeffects corresponding to the polymorphic transition of n-nonadecane and the melting of the eutectic. The calculation of the eutectic coordinates by the UNIFAC Dortmund method showed the smallest deviation in the composition of the eutectic alloy from the experimental data. For an alloy of eutectic composition, the specific enthalpy of melting, the molar values of the entropy and enthalpy of melting, the volumetric specific enthalpy of melting, and the density for standard conditions are determined. This two-component system was studied by low-temperature differential thermal analysis. The eutectic melt can be used in industry as a heat carrier. Also, the eutectic composition of the diphenyl-n-nonadecane system under study can be used as a working fluid of a heat accumulator. For citation: Kazakova A.I., Yakovlev I.G., Garkushin I.K. Phase equilibrium states in a two-component diphenyl-n-nonadecane system. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 6. P. 46-53. DOI: 10.6060/ivkkt.20236606.6733.

About the Possibility of the Hydrate Formation in Subpermafrost Aquifers Saturated with Calcium Chloride-Type of Waters

In this work, we consider the results of studying the natural gas hydrates formation in porous media saturated with fresh water and sodium chloride solutions of 5, 10, and 15 wt%. at a pressure of 8 MPa. The studies were carried out by the method of differential thermal analysis. It was found that the presence of salts in porous media reduces the degree of water conversion into hydrate, as well as the rate of the gas consumption in the process of the hydrate formation

SYNTHESIS OF SUPER-BRANCHED POLYGLYCERIDES OF SACCHARIN-6-CARBOXYLIC ACID

By polycondensation of triglyceride of saccharin-6-carboxylic acid with some aliphatic diamines, the thermal-stable super-branched polyestersulfoimides – polyglycerides of saccharin-6-carboxylic acid have been obtained. The structures of the synthesized compounds have been confirmed by data of the IR spectroscopy. The yield of the purposeful product was 80–83%. It has been found that the synthesized polyglycerides are well dissolved in polar aprotonic solvents. The thermal stability of the obtained compounds was studied by a method of differential-thermal analysis on derivatograph of system ʺPaulik-Paulik-Erdeyʺ. The derivatographic investigations showed that the synthesized polyglycerides have high thermal stability, decreasing with the growth of length of the aliphatic fragment in their composition. For comparative estimation of the thermal and physical-mechanical indices of the synthesized polyglycerides, the corresponding indices of the industrial polyesterimide Zellamid 1000 have been also given. It has been found that the obtained polyglycerides do not concede to industrial polyesterimides on physical-mechanical indices, but exceed them on thermal stability

Solid-state synthesis of ZnMn2O4 spinel: Sequence of phase transformations, thermal stability, localization and charge state of manganese ions in the intermediate and final reaction products

This paper presents data on the solid-state synthesis of spinel ZnMn2O4, one of the leading promising materials for numerous practical applications. The evolution of the phase composition and charge state of manganese ions during the solid-state synthesis of ZnMn2O4 in air from ZnO and Mn2O3 has been studied. Using differential thermal, thermogravimetric, and X-ray diffraction analysis methods it has been established that, at a temperature of about 700 °C, an insignificant amount of ZnMn2O4 is present in the mixture with the initial oxides. During further heat treatment ZnMn2O4 interacts with Mn2O3 to form the solid solution based on ZnMn2O4. In parallel with this process, in the temperature range of 800–850 °C, ZnMn2O4 reacts with ZnO to form the compound ZnMn4+O3. It has been shown that heat treatment at 880–1180 °C leads to the formation of the final single-phase product – ZnMn2O4. Using diffuse reflectance spectroscopy, XPS, and FT-IR methods, the charge state and localization of Mn ions in the intermediate and final synthesis products have been determined. It has been shown that in the Zn1-xMn2+xMn3+2O4 solid solution Mn2+ ions are localized in the tetrahedral positions and Mn3+ ions in the octahedral positions of the structure. In the final single-phase product, ZnMn2O4, the tetrahedral positions are occupied only by zinc ions, and the octahedral positions are occupied only by Mn3+ ions. It has been established that ZnMn2O4 is stable up to 1300°С. Upon reaching this temperature, ZnMn2O4 decomposes into ZnO and Zn1-хMn2+хMn3+2O4.

Research of innovative adsorbents in cottonseed oil refinement technology

Based on the results of a comprehensive research of the nature and colloid-chemical properties of selected local clays before and after their acid activation, it has been established that Shafrikan bentonite (Bukhara region) and Mayskiy clay (Tashkent region) are promising raw materials for obtaining effective adsorbents for the oil and fat industry. The new types of adsorbents in cottonseed oil bleaching technology have been studied. The main sorption properties of local clays as adsorbents have been determined. The dependence of the chromaticity of cottonseed oils on the sorption properties of innovative types of adsorbents has been established. The temperature limits of the first, second and third “effect” for selected samples of local clays has been established by the method of differential thermal analysis. A spectral method has been developed for quantitative evaluation of the selectivity of adsorbents in the bleaching of vegetable oils, in particular cottonseed oils. Mathematical models have been developed for obtaining activated adsorbents from local clays, and based on them the optimal modes of recommended processes have been selected. The intensifying role of vacuum in the production of activated adsorbents from local clays has been established.

Metallurgical aspects in production of nickel high-temperature alloy disk blanks obtained by hot forging

The main metallurgical aspects that must be taken into account in the production of disk blanks with a diameter of up to 300 mm by hot forging are presented using the example of a nickel high-temperature alloy of the VZh179 type. The temperatures of phase transformations in the material under study are determined using the method of differential thermal analysis. On the basis of these data, the temperature-time modes of heat treatment of disk forgings are selected. The computer simulation of the hot forging process is carried out in the QForm 3D software package. The distribution fi elds of temperature and intensity of plastic deformation over the forging volume are determined. The optimal modes of hot forging and heat treatment of a nickel heat-resistant alloy are selected, which ensure high manufacturability and a level of mechanical characteristics that meets the requirements of technical specifications.